The block won't change color when I click play?

game.Workspace.Part.LocalScript
color = Really Red

Also, what is the best way to test a script?

Hello there. This is a very easy mistake to make! You did not use correct format. Lets re-write this entire script. You need to use BrickColor.new statement. Make a part you want to change color, then add a script.

local changemycolor = script.Parent --This locates the part.

changemycolor.BrickColor = BrickColor.new("Really red") --This finds the variable changemycolor, and changes the brickcolor of changemycolor to Really red.